A Real Life Quantum Delayed Choice Experiment 

"Sorry, I'm late from the party. Come and meet me in the future?"

D-mail?

Which timeline won’t change? Past, present, or future (universe branch)? Many Worlds Interpretation of Quantum Mechanics fixes the paradox.

well 9 years left

yes, the explanation seems hard to accept because it makes you think there is instant action at a distance, but it just works

Yeah most def the left atoms quark nuetron start def will lead to orange juice

@Bobby T, in the double-slit experiment, particles are detected on the screen. Are you saying that means they travelled as particles even when producing interference patterns?

@Bobby T, if it had to be a particle some amount of time before hitting the screen, wouldn't that change the pattern? is the diffraction pattern on the screen not consistent with it travelling as a wave all the way up to the screen?

@Bobby T, if they travelled along straight trajectories, wouldn't there be a shadow in the middle because of where there is opaque between the two slits?

LoL

What happened to your brain matter after that happened 🤔

@@lotsoffreetime8392 it blew even harder after i had to write two 2000 words paper on different interpretations of quantum mechanics + the quantum erasor

@@chrishbeatboxing2291 My guess is, you didn't pass the class, or did you?, we cant know until you show proof of the certificate

@@chrishbeatboxing2291 after reading your comment i lose some of brain cell 🙃

where do you see real life experiment ? any single foton emiter ? any foton detector ?What about 1000 kilometer long photon of 300hz frequency ?

@Eric C pseudo intellectual detected. Do u even realize that the point is to use 1 photon because it cant take 2 paths at the same time? If u have more than 1 than each of them can take different path

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Exactly, but Quantum mechanics is open to interpretation. Even though they all agree on the predicted outcome of experiments, they disagree on what the wave function represents. And then you get, in my point of view, ridiculous interpretations, like the one presented on the video or many-worlds interpretation.

So why does the interference pattern appear in the double slit experiment, even when shooting separate particles, one by one?

@@DaP84 It's the same reason. The particles behave as wave functions, I mean each particle individually so it doesn't matter if it's one at a time or one billion at a time, and this wave function, for each particle, spreads over all space. You could imagine It like a water wave, even though they don't behave exactly the same. So this wave function interferes with it self, causing the interference patterns, the analogy with other types of waves here is basically perfect. I don't think anyone disagrees with what I just said, but the problem is: "what does the wave function represent ?". Roughly speaking, the answers to this question are called interpretations. The most popular one is the Copenhagen interpretation, where the wave function represents an amplitude of probability, but there are many many others. A very interesting one is the de Broglie-Bohm interpretation.Truth is that it doesn't really matter, since they all agree on the outcome of the experiment and can't be tested, but it's interesting conversation

@@joaofelipecamargopinheiro4230 exactly. Why do people always make it sound more complex than it is?

It's not. That's like saying an mp3 and a singers voice and the microphone and the speaker are one.

@@howiegruwitz3173 exactly. the wavefunction models quantum behavior BEFORE it is measured. measured quantum behavior is necessarily eigenstates of the wavefunction, which are particle-like in a sense.

It sounds like he's being molested as he talks

True

Wow... how can I miss this core concept during college!?

A well known fact but never it had been stated so beautifully. Amazing.

You make physics enjoyable like art.

Light is both wave and particle. Wave-only explanation fails to explain photoelectric effect, especially the threshold frequency part.

@@JohnTan You are making the absolute declaration that the photoelectric effect is proof of the existence of particles. So, you claim that the photoelectric effect is evidence of a 3 dimensional substance, travelling across space and time, and itself occupying space and mass. A "particle" of matter. OK, so what is the photoelectric effect? The photoelectric effect is the phenomena of electrons changing energy state by quantised steps, and not according to an infinitely variable scale. When electrons change energy state, either absorbing or emitting energy, they do so in strictly quantised amounts. Why do we believe that this behaviour is associated with particles? Well, it can be. If we take a bullet with a known mass, and we shoot it with a known velocity at another object, we can calculate the kinetic energy in imparts to the other object. Both bullet and object are "particles", in effect. So, by using a kinetic model of energy, where mass and velocity are deterministic of all reality, we can understand "particles" as capable of transporting energy across space, and exchanging energy with other particles. This is why we suppose that the photoelectric effect might be the result of particle interaction. It fits the kinetic energy model of the universe. Yet, it is demonstrably wrong to declare that all exchange of energy in quantised form involves the interaction of particles. Consider the humble raindrop, and phase change. Water vapour condenses into droplets, each droplet representing a quantised amount of energy. That is to say, it takes an exact and quantised amount of energy to make one droplet of a given size from water vapour. Even though we understand that many millions of water molecules are combining to give each single quanta of energy emitted by the condensation of each individual rain drop, we describe the cumulative effect of all these molecules as a single quanta of energy, that being equal to one raindrop. And this is, in fact, a quantised event. Each droplet actually exists, and each droplet really does have it's own "quanta" of energy that dictates it's state, as either a liquid or a gas. And thus, every droplet of water has it's own "photon" particle, if we accept that quantised exhibitions of energy are hard proof of particles that transport this energy exchange. It's rather magical a mysterious, the way phase change between gas and liquid exhibits apparently arbitrary examples of quantised energy. Even so, for the purposes of the discussion of light, we have now established that water droplets must have particles associated with them, particles that hit water vapour and cause it to change energy state. Why? Well, we've established that any quantised exhibition of energy exchange is hard proof of the existence of particles, objects with 3 dimensions and mass and so on, carrying this quanta of energy from one place to another place. Therefore, as we have raindrops occurring, we have proved that raindrop photons must exist, and thus there must be these particles, with specific size and mass, capable of exchanging the energy needed to vaporise and condense water droplets. We are not permitted to argue that phase change occurs due to temperature and pressure. No, we have a quantised exhibition of energy, and we have declared that such a thing is hard proof of particles that transport the whole sum of this quanta of energy as kinetic energy. Now, a thoughtful person might try to argue that a change in temperature causes the droplet to form (or to disappear) because many "photons" of energy are being exchange by molecules. This argument does not explain why, or how, many small particles can suddenly exhibit the behaviour of one single large particle, but even so it does bring us back to discussions of particles being the carriers of energy, to and fro, and so it cements the idea that where we see energy exchange, we see particles hitting each other. Yet, what if we cause the phase change and water droplets formation by changing pressure only? How does the interaction of particles now explain the quantised change in energy state? A change in pressure doesn't even involve the exchange of many photons. Suddenly, we are faced with quantised exhibitions of energy exchange, without any apparent interaction of kinetic energy between particles. The point here is that "quanta" of energy, or discreet packets of energy, are analogous to the exchange of kinetic energy between particles of known mass, but they are hardly proof of such things. Yes, it is true, when we examine particles in the world, we can observe quantised transfers of energy. It is a bold claim, however, to argue that every quantised exchange of energy is hard proof of one particle striking another. This desire to perceive the world as substantive objects striking other substantive objects, this article of faith in the kinetic reality of things, is very ancient. Newton was criticised for suggesting the existence of gravity, because gravity violates the idea of a mechanical universe, a place where all things touch other things, and all exchange of energy is always kinetic. So does electrostatic force, but gravity violated the mechanical universe worldview long before electrostatic force did so. Anyway, that's what I think about that. I don't think one can convince the hard core particle people. Those folks are extremists. They are beyond reason. The believe in neutrons, and pineapple on pizza, and every other kind of perversion and wickedness. We just have to make the sign of the cross when folks get their particle fever on, and say "There, but for the grace of god, go I."

Doesnt even have to be one path, the interference is due to the two waves being misaligned, not due to the existance of two waves by themselves

I'm not sure either that this gives any meaningful result in air, it has to be done in a vacuum. I suspect this experiment is an explanation model, not indented to be used to test anything.

@@Tore_Lund As far as I understand it's equally valid in air as in vacuum. The experiment is to test if photons are particles or waves (spoiler: they're ALWAYS waves, even when you measure them as particles.) The problem with removing the second beam splitter is that it doesn't tell you that it's NOT a wave and only transited one path as a discreet particle. It only tells you that it DID transit the blue path.

@@mduvigneaud Air does interact with photons, there is diffraction which means that the are absorbed and reemitted. However as the distance is short, the majority of photons might not interact with any air molecules?

@@Tore_Lund From what I understand that's a bit of a misconception: they aren't absorbed and re-emitted. They're diffracted because they are waves. The interaction with air molecules is also not relevant to trying to determine if they are particles or waves.

@@mduvigneaud It depends of the molecule; like with spectrography, specific wavelengths are absorbed and reemitted, in this case, green might be be able to pass through, but if there is an interaction, the result is the same as when the light hits the screen, the wave function collapses before it ever reaches the screen.

You can. It just takes a while.

@@samlevi4744 true that😂

Derp

@@mr.loveandkindness3014 We know what we know based on reason and evidence. Empiricism is the branch of philosophy for these scientific discoveries.

Why can't you? Apply yourself. With the plethora of great RU-vid channels on the subject it's actually mot as hard to get into Quantum Physics anymore. Just gotta open your mind to some crazy shit haha

yes, more about the quantum eraser please!

I think the wider one will boil more quickly because you have a larger surface area in direct contact with the flame.

You're talking about a different experiment. The Delayed Choice Quantum Eraser experiment. This one is the Wheeler Delayed Choice experiment.

very few people see how relativity requires the photon to have simultaneous contact with the emitting atom and the absorbing atom even though we see time pass, the photon does not. If time doesn't exist for the photon, why do we see it as having a frequency and a wavelength? I never understood that.

@@ninehundreddollarluxuryyac5958 Well, you can look at frequency or wavelength as properties which describe the amount of energy transported by the photon. The higher the frequency is (shorter wavelength) the more energy is being transported.

_"There's simply no time for the beam splitter to move once the photon started its journey."_ - it is more correct to state that the photon _does not notice_ the beam splitter moving, because it happens in the same instance of time.

“They exist in all points of their trajectory simultaneously within a single point in time” what does that say about a video.. I mean , when a camera captures video footage, it’s splitting the incoming light into individual photons that are recorded and stored as a series of frames… You’re compactifying time. Like putting your finger in a laminar flow..

Photons don’t have a perspective. Considering a photon’s perspective is like considering marshmallowing an umbrella at lamp o’ clock in the morning. There is no discernible meaning to it. Special relativity dictates that the speed of light is the same in all reference frames. If light had a rest frame, it would be moving at the speed of light in its own rest frame, which is absurd.

I agree, there must be something else, though QM explains it well.

If you've seen the double polarizer experiments where you put a rotated polarizer in front of two polatizers completely blocking the light to somehow allow the light through. The physical experiment he set up is not really showing anything different than that because hes not using single photons.

So I’m not the only one who felt like this could have been explained better? Mind you, still grateful for the otherwise excellent and free videos! :-)

@@lucbloom just look up "john wheeler" on youtube the first video should be a 2 min video of him talking about the delayed choice. He puts it in plain English.

@@williamcrosby1061 I find the videos putting it in layman's terms make it sound more magical than it appears to actually be.

@@goldenalt3166 right... because retrocausality is very non magical... you obviously didn't watch john wheelers video either or you definitely would not have said that.

@@williamcrosby1061 _"just look up "john wheeler" on youtube"_ - I did that. The video does not make it very clear at all. _"because retrocausality is very non magical"_ - no retro-causality is necessary, unlike Wheeler seems to imply.

The many world interpretation makes little to no actual sense in reality. John wheeler explains it perfectly well without any mumbo jumbo in less than 3 mins it's the first video when you youtube his name.

The pattern will appear in both directions as half of the wave is reflected while the other half passes through

@@akashvishwanath1159 That seems reasonable, but I'm not sure that it's actually the case. (I could be wrong though; and thank you.)

if the distances are exactly equal on both paths, the middle of the interference pattern is dark on top and bright on the right.... the interference pattern appears because the photons are not exactly parallel and thus have slightly different path length on the two ways through the apparatus

@@deinauge7894 Thanks, I think I understand. So, over time, a photon detector centred to the right would register but one centred at the top would not? (This must be what I had been thinking of!)

​@@rogerkearns8094 _"So, over time, a photon detector centred to the right would register but one centred at the top would not?"_ - correct for the drawings, because the light source is to the left in the drawings. For the experimental setup, it's the other way around, because the light source is at the bottom in those.

The 2 halves, white and yolk became one... The yolks on you🤣

@@terrafirma9328 😂😂😂👍

That should tell you stop doing the drug...science🥴

I’m convinced we are simply misunderstanding something at a fundamental level and that all this stuff is far less magical than it seems. If you asked someone from 1000 BC to walk into an air conditioned room in the middle of summer and showed them a box you did it with, it would seem like magic. If you were to show them how refrigerants work it would seem less incredible and interesting.

This is not the delayed choice quantum eraser, but rather Wheeler's delayed choice experiment. The retro-causal nature of the experiment depends on there being a choice in the first place. The phenomenon being explored here is called "contextuality". That means the measurement itself determines the property of the quantum object being detected. This is a central property of quantum theory.

пока что нет правил запрета передавать информацию во времени обратно!)))) биткоин в помощь!)))

Aether

@@bagnon stop it